Opposition to immigrants is based on the requirements of the capitalist class to maintain both a source of intra-class conflict (to divide the working class) as well as to create a desparate sub-category of the working class that fears systemic violence and expulsion, and is thus more easily exploitable by capitalists. Critical thinking isn’t the barrier, republican voters buy into this as a party primarily backed by a combination of the petite bourgeoisie and the haut bourgeoisie.

You’re placing too much of an emphasis on the ideas of society without looking at where these ideas come from. It isn’t lead poisoning, it’s from the way we produce and distribute. That doesn’t mean ideas do not play a part, that would be reductive, but the primacy exists with the base of society, the economic foundation.

Even if the working class voted in their self-interest, they would not be able to establish socialism, which is necessary. It would lead to a third party victory, and a failure of the third party to change capitalism into socialism piece by piece.